body {
    font-family: Arial, sans-serif;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    height: 100vh;
    margin: 0;
    background-color: #fff;
}

.logo-container {
    margin-top: 10vh;
    margin-bottom: 20px;
    text-align: center;
}

.logo {
    max-width: 200px;
    height: auto;
}

.message {
    text-align: center;
    padding: 20px;
    background-color: white;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0,0,0,0.1);
}

@media (max-width: 600px) {
    .logo {
        max-width: 120px;
    }
}

.grade-buttons {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 24px;
    margin: 40px 0;
    flex-wrap: wrap;
}

.grade-btn {
    width: 80px;
    height: 80px;
    background: #1976d2;
    display: flex;
    align-items: center;
    justify-content: center;
    text-decoration: none;
    border: none;
    border-radius: 50%;
    box-shadow: 0 2px 6px rgba(0,0,0,0.08);
    transition: transform 0.2s;
}

.grade-btn span {
    color: #fff;
    font-size: 2.5rem;
    font-weight: bold;
    text-shadow: 0 2px 4px rgba(0,0,0,0.15);
}

.grade-btn:hover {
    transform: scale(1.3);
}

@media (max-width: 600px) {
    .grade-buttons {
        gap: 16px;
    }
    .grade-btn {
        width: 64px;
        height: 64px;
    }
    .grade-btn span {
        font-size: 2rem;
    }
}

@media (max-width: 500px) {
    .grade-buttons {
        flex-direction: row;
        flex-wrap: wrap;
        justify-content: center;
    }
    .grade-btn {
        flex: 1 1 40%;
        margin-bottom: 12px;
    }
}

.main-title {
    color: #1976d2;
    text-align: center;
    margin: 24px 0 0 0;
    font-size: 2.5rem;
    font-weight: bold;
}